Methodology

The list is made up of the games with the biggest change in price compared its average price in the last two years. We use the standard deviation for the prices to eliminate games that naturally have volatile prices.

For example, a game has an average price of $10 and a standard deviation in this price of $1. 96% of the time prices will be within $8 and $12. If during the next three months the price jumps to $14, then $15, and $16 after that we can be very confident the price increase is statistically significant.

@anonymous - Thanks for letting us know about this problem. The charts were being updated, but I forgot one small change on the website to make those changes visible. I made that change and you can now see the prices with September and October included.